DE102021210240A1 - Clearance adjustment for wet-running multi-plate clutches or brakes in a drive train of electrically driven vehicles - Google Patents

Abstract

The invention relates to a switching element for actuating wet-running multi-plate clutches or brakes, in particular in the drive train of electrically driven passenger cars. The task of finding a new way of adapting a tight clearance 17 of wet-running brakes or clutches, which reduces the actuation work and power required for rapid filling, is achieved according to the invention by using a shifting device 1 with a disk pack of axially displaceable inner and outer disks 2, 3, which can be compressed, a seat valve 11 can be controlled in such a way that a defined residual pressure is maintained in the volume of the disk set when the inflow of cooling oil to the disk set is blocked by the seat valve 11, and a pressure generated in the chamber 9 of the switching element piston 10 Oil pressure can be adjusted by means of control via actuating valves for the pressure oil of the switching element 1 against the defined residual pressure of the cooling oil in the disk pack so that when learning a pressure point of the preload spring force of the switching element piston 10 for an opening state of the switching element 1, a narrower clearance 17 compared to the rigidity The preload suspension can be adjusted.

Description

The invention relates to a switching element for actuating wet-running multi-plate clutches or brakes, in particular in the drive train of electrically driven passenger cars, comprising a disk pack with inner and outer plates, an inner plate carrier on which the inner plates of the plate pack are arranged so that they can be displaced axially, an outer plate carrier on which the The outer disks of the disk pack are arranged so as to be axially displaceable, with the disk pack being compressible by means of a switching element piston when the switching element is actuated and coming to rest on an end disk arranged on the side of the disk pack facing away from the switching element piston, with a seat valve allowing cooling oil to flow to the disk pack when the switching element is closed and blocks the inflow when the switching element is open.

The field of application of the invention is in the automotive industry, primarily electric or hybrid vehicles, in particular for increasing the efficiency of the electric drive train.

In the current state of the art of electric or hybrid vehicles, great efforts are being made to better integrate the braking system in particular into the electric drive train in the electric drive concept and thereby achieve synergy effects and increases in effectiveness.

In general, with disc brakes - regardless of whether they have a brake pad or a disk pack - the drag losses that define the delay in effectiveness from the open to the closed brake pad or disk state are always undesirable and must therefore be minimized as a matter of urgency. In addition to the primary influencing variables, such as medium in the air gap (air clearance), lining width, number and diameter of the friction surfaces, and the secondary influences, such as friction lining use and lining surface, there is also the air clearance (distance between the brake pad and brake disc in disc brake systems or lamellae in multi-disk brakes or clutches). particular importance because a distance between the brake lining and the brake disc is indispensable for the (unbraked) circulation of the brake disc, but on the other hand the clearance leads to an increase in the braking distance when the brakes are actuated, which, in the case of a hydraulic brake system, is referred to as the brake response time (time to overcome the clearance ) can be about 0.1 to 0.2 seconds.

The necessary clearance is usually set by a return spring acting in the opening direction of the actuating piston. However, this creates the disadvantage that the piston-cylinder arrangement has to be dimensioned larger by the restoring spring force and that when the actuating piston is subjected to a clutch closing pressure, the actuating path of the clearance must first be bridged in a pre-filling phase before the lamellae come into force engagement.

In contrast, in purely electric or hybrid drive trains, particular attention is paid to the energy efficiency of the drive train, since the efficiency can be read directly from the battery life.

So far, wet clutches and brakes have been actuated by mechanical or hydraulic switching elements. As a rule, the clearance for wet-running clutches is set in such a way that it is in the efficient drag torque-optimized range, and the safe starting position is positioned by a piston contact with spring forces. The same applies to multi-disk brakes, whereby the drag loss as a time delay in the braking effect is to be minimized.

Numerous solutions for shifting elements for reducing the drag torque have become known in the prior art for disk packs of clutches or brakes in the transmission of a drive train.

That's it DE 10 2014 226 517 A1 a switching element of a transmission is known, which has a valve which, when the switching element is open, blocks the flow of cooling oil to the disk set and, when the switching element is closed, releases the flow of cooling oil to the disk set. A disadvantage of such a system is that the disks of the disk pack through which cooling oil flows can stick to one another when the switching element is open due to the capillary effect of thin oil films between the disks, resulting in an undesirable drag torque.

Furthermore, in the DE 10 2019 218 519 A1 discloses a switching element for a disk pack with inner and outer disks, in which the inner and outer disks are each attached to their separate carriers in an axially displaceable manner and a piston that can be hydraulically displaced in a cylinder is provided for compressing the axially displaceable disk pack in the closed state of the switching element, which presses the plate pack against an end plate as an abutment. The end disk has a valve seat for a valve that allows the inlet of cooling oil when the switching element is actuated and blocks it when the switching element is open. Thus, when the switching element is actuated, the valve opens the disk pack is effectively cooled by the cooling oil, while the drag torques are reduced when the switching element is not actuated and due to the lack of cooling oil when the valve is closed. Furthermore, the drag torques can be reduced further if an elastic element is arranged between the adjacent inner disks and/or the adjacent outer disks, which element separates the inner and outer disks when the cooling oil flow is blocked.

The desired tight clearance is problematic, especially with a higher number of lamellae, because the strokes can become large and fluctuating as a result of component tolerances. In the case of large strokes, the actuation work required also increases and thus the power required for fast filling, which is detrimental to energy efficiency.

The object of the invention is to find a new way of setting a desired tight clearance of wet-running brakes or clutches that reduces the required actuation work and the associated performance for rapid filling, especially for higher numbers of disks.

The task is a switching element for actuating wet-running multi-plate clutches or brakes, in particular in the drive train of electrically driven passenger cars, comprising a disk pack with inner and outer plates, an inner plate carrier on which the inner plates of the plate pack are arranged so that they can be displaced axially, an outer plate carrier on which the outer disks of the disk pack are arranged in an axially displaceable manner, with the disk pack being compressible by means of a switching element piston when the switching element is actuated and coming to rest on an end disk arranged on the side of the disk pack facing away from the switching element piston, a seat valve which is inserted into the end disk, the When the switching element is open, the seat valve blocks an inflow of cooling oil to the disk pack and when the switching element is closed it releases the inflow, and elastic elements, which are at least between adjacent I Inner disks or between adjacent outer disks of the disk pack are arranged, for separating outer and inner disks of the disk pack when the switching element is open and the inflow of cooling oil to the disk pack is blocked by the seat valve, solved in that the seat valve can be controlled in such a way that a defined residual pressure of the cooling oil is maintained in the volume of the disk pack, which essentially replaces a preload spring force required to return the shift element piston when the inflow of cooling oil to the disk pack is blocked by the seat valve, and that an oil pressure generated in the chamber of the shift element piston is controlled via Actuating valves for the pressure oil of the switching element can be adjusted against the defined residual pressure of the cooling oil in the disk pack, so that when learning a pressure point of the preload spring force of the switching element piston for an opening state of the switching element, a narrower Lüftsp iel is achievable and adjustable relative to the stiffness of the preload suspension.

One or more elastic elements, which are present for separating the outer disks of the disk pack, are advantageously used as the preload spring.

In this case, the elastic elements can preferably be made of spring elements made of elastomer or other elastic elements.

Alternatively, the elastic elements are expediently designed as ring-shaped wave springs made from corrugated flat or round wire.

Advantageously, the control of the actuating valves for the pressure oil of the switching element is designed to vary the size of the clearance depending on the situation.

The control of the actuating valves for the pressure oil of the switching element can be set up to adjust the size of the clearance, preferably depending on critical frequency ranges that can stimulate the lamellae to move.

Furthermore, when controlling the actuating valves for the pressure oil of the shifting element for the adjusted setting of a narrower clearance, the installation space of the cylinder for the shifting element piston can be shortened.

The core idea of the invention is to “lock in” a residual pressure in a hydraulically sealed actuation system for wet-running clutches with seat valves. At least one preload spring is still required, against which the hydraulics of the actuation system work, but when teaching the pressure point (so-called touch point) you can maintain and set an open position for teaching in an optimal clearance against the stiffness of the preload springs. The at least one preload spring can preferably be designed as one or more springs that are also used to separate the steel laminations.

The clearance can also be adjusted by variable control options via the actuating valves varies depending on the situation and the clearance can be adjusted in critical frequency ranges that stimulate the natural frequencies of the slats in order to limit the undesirable side effects.

Furthermore, the clearance can also be optimally adjusted, which means that the installation space for the piston strokes can also be shortened.

The invention provides a new possibility for setting a desired tight clearance of wet-running brakes or clutches, which reduces the required actuation work and the associated performance for rapid filling, in particular for higher numbers of disks.

• 1: eine schematische Darstellung eines erfindungsgemäßen Schaltelements zum Betätigen oder Öffnen eines nasslaufenden Lamellenpakets, wobei ein Sitzventil für den Kühlöldurchfluss durch das Lamellenpaket beim dargestellten Zustand des nicht betätigten Schaltelements geschlossen ist und einen Restdruck des Kühlöls im Volumen des Lamellenpakets einschließt,
• 2: eine schematische Darstellung des erfindungsgemäßen Schaltelements von 1, dargestellt im Betätigungszustand des Schaltelements mit geöffnetem Sitzventil für den Kühlöldurchfluss.

The invention is explained in more detail below using exemplary embodiments and drawings. It shows:

• 1 : a schematic representation of a switching element according to the invention for actuating or opening a wet-running disk set, with a seat valve for the cooling oil flow through the disk set being closed in the illustrated state of the non-actuated switching element and including a residual pressure of the cooling oil in the volume of the disk set,
• 2 : a schematic representation of the switching element according to the invention from FIG 1 , shown in the operating state of the switching element with the seat valve open for the flow of cooling oil.

1 shows a schematic representation of a switching element 1 for actuating or opening a wet-running disk pack for clutch or braking processes in the drive train of an electric or hybrid drive, which is in the non-actuated (ie opened) state. The switching element 1 comprises a disk set with inner disks 2 and outer disks 3. An inner disk carrier 4 has a toothed profile 5 on its outer peripheral surface, in which the inner disks 2 are arranged in a rotationally fixed but axially displaceable manner. An outer disk carrier 6 has a toothed profile 7 on its inner peripheral surface, in which the outer disks 3 are arranged in a rotationally fixed but axially displaceable manner.

In this example, the inner disks 2 are designed as lining disks, each lining disk consisting of a steel disk with a friction lining attached on both sides. The friction linings are designed to be continuous and firmly connected to the steel disc, for example by means of an adhesive connection. The outer disks 3 are designed here as steel disks without a friction lining. An inverted design of lining and steel plates is alternatively possible.

In a further embodiment of the disk pack, the inner and outer disks 2, 3 can be designed as single-side disks, i.e. both the inner disks 2 and the outer disks 3 are each provided with a friction lining on one side, while the other side designed as a steel plate.

An oil channel is provided in a cylinder 8 through which pressure oil can be introduced into a chamber 9 . The chamber 9 is delimited in the cylinder 8 by a switching element piston 10 . When switching element 1 is open - as in 1 shown - the switching element piston 10 is held in a starting position by means of a restoring spring, not shown, which can be designed for example as a plate spring, the inner and outer disks 2, 3 being arranged at a certain distance from one another without frictional engagement.

On the side of the disk pack facing away from the shifting element piston 10 , an end disk 16 of the shifting element 1 is formed by the outer disk carrier 6 . The outer disk carrier 6 shown here, on the one hand, accommodates the outer disks 3 of the disk set in an axially displaceable manner and, on the other hand, forms the axial stop for the compressed disk set.

A seat valve 11 is arranged in the end disk 16 and has a valve element 12 which is arranged in a cooling oil channel 14 of the end disk 16 . The valve element 12 is preferably mushroom-shaped and comprises a disk or plate element and an extension which, when the seat valve 11 is closed, protrudes into a cylinder chamber formed by the outer disk carrier 6 in which the disk set is arranged. The end plate 16 has a valve seat 13 on which the valve element 12 comes to rest when the switching element 1 is open when it is acted upon by a cooling oil pressure prevailing in the cooling oil channel 14 and thus blocks the inflow of cooling oil to the disk set. The valve seat 13 is formed here by an annular disk which is connected to the end disk 16 by pressing, for example. However, the ring-shaped disk can also be connected to the end disk 16 with a material connection, such as by welding or gluing, or by means of a screw connection. As an alternative to this, the ring-shaped disk can also be fixed in the end disk 16 by means of a retaining ring.

At the beginning of a switching process, in which the switching element 1 is to be closed, is Pressure oil is introduced into the chamber 9 and the switching element piston 10 is moved towards the disk pack under the pressure influence of the pressure oil. The axial displacement of the switching element piston 10 during pressurization causes the distance between the inner disks 2 and the outer disks 3 to be reduced until the inner and outer disks 2, 3 engage frictionally, as is shown in FIG 1 is shown. When the frictional engagement of the inner and outer disks 2, 3 occurs, there is still a speed difference between the inner and outer disks 2, 3. Due to the speed difference between the inner disks 2 and the outer disks 3, a great deal of heat is generated at the beginning of the frictional engagement.

With increasing pressure of the pressure oil in the chamber 9, the shifting element piston 10 is then moved further in the direction of the end plate 16 until the speed difference disappears and a non-positive connection of the inner and outer disks 2, 3 prevails and the plate pack is pressed onto the end plate 16 of the shifting element 1 will what in the 2 is shown.

Before the disk set comes into contact with the end disk 16, the seat valve 11 arranged in the end disk 16 is moved in the axial direction by the disk set, in particular by the outer disk 3 closest to the seat valve 11, against the cooling oil pressure prevailing in the cooling oil channel 14. As a result, the valve element 12 is released from the valve seat 13 and the inflow of the cooling oil prevailing in the cooling oil duct 14 in the direction of the disk set is released. As a result, when the switching element 1 is closed, the heat stored in the disk pack can be dissipated.

The end disk 16 also has an annular groove 15 for cooling oil to flow through the disk pack. The outer disks 3 designed as steel disks have at least one passage opening 21 at their radially outer end. The annular groove 15 of the end disk 16 and the at least one passage opening 21 provided in the outer disks 3 are arranged in alignment with one another here. This allows cooling oil to flow axially through the disk pack when the switching element 1 is closed. After flowing through the plate pack, the cooling oil is fed to a cooling oil reservoir. A plurality of passage openings 21 are preferably provided in the outer disks 3 , which are located on a circular ring (not visible here) of the outer disks 3 .

Since the disk pack is not cooled when the switching element 1 is open, drag torques generated by the switching element 1 are low. However, if the switching element 1 is transferred from a closed state to an open state, then the disks of the disk pack can stick to one another when the switching element 1 is open, particularly at low speeds, due to a capillary effect of thin oil films between the disks of the disk pack, resulting in an undesirable drag torque . The drag torque can be reduced by elastic elements 20 between the inner and/or outer disks 2, 3 for separating or separating disks 2, 3 adhering to one another. The elastic element 20 can, for example, be ring-shaped or partially ring-shaped or be designed as an elastically deformable plastic ring. Partial ring-shaped here describes a partially open ring. Alternatively, the elastic element 20 can be designed as a wave spring made of annularly corrugated flat or round wire.

The elastic element 20 is used on the one hand for the axial positioning of disks of the disk pack when the switching element 1 is open, and on the other hand for improved guidance of cooling oil through the disk set of the switching element 1 when the switching element 1 is closed. Thus, by means of the elastic elements 20, a reduction in the drag torque acting when the shifting element is open and improved cooling of the disk pack when the shifting element 1 is closed is achieved. However, this usually results in an unacceptably large clearance 17 between the inner and outer disks 2, 3, since a clean separation of the inner and outer disks 2, 3 must be ensured, particularly in a disk pack with many disks, despite manufacturing tolerances.

According to the invention, it is therefore provided that, in order to separate the inner and outer disks 2, 3 of the disk set that are adhering to one another, the seat valve 11 is dimensioned or designed so that it can be controlled in such a way that a defined residual pressure of the cooling oil is “locked in” in the cylinder formed by the outer disk carrier 6 around the disk set. which, although it cannot completely replace the preload springs usually present for prestressing the switching element piston 10, such as the return spring or the elastic elements 20, can be made significantly smaller.

However, the main advantage for setting a narrower clearance 17 is that the pressure of the pressure oil in the chamber 9 of the shifting element piston 10 can be set more precisely against the defined residual pressure of the cooling oil in the disk pack by means of control via the actuating valves for the pressure oil of the shifting element 1. When teaching the pressure point (so-called touch point) of the preload suspension of the Switching element piston 10 receive and set an open position of the switching element 1 for teaching the optimal clearance 17 against the stiffness of the preload suspension. In this case, the preload springing can advantageously be carried out without the otherwise usual restoring spring of the switching element piston 10 alone with the elastic elements 20 for separating the inner and outer disks 2, 3.

Due to the variable options for controlling the actuating valves of the switching element 1, the clearance 17 can also be varied depending on the situation and thus, e.g.

With the embodiment variant of the invention described above, the preload spring-dependent, generously dimensioned adjustment of the clearance 17 for wet-running disk packs for clutch or braking processes is eliminated, which, in addition to the changeover to wet multi-disk clutches or brakes, above all an adjustment of the clearance 17 based on a defined retention in the disk pack Residual pressure for the open state of the switching element 1 is used to minimize the time delay due to drag losses due to large clearance 17 and improve the energy efficiency of the clutch or brake actuation.

During a teach-in process of the so-called touch point, by which the clearance 17 to be set is determined, the clearance 17 can thus be adjusted independently of mechanical preload springs of the switching element piston 10 or elastic elements 20 for lamina separation by means of controllable valves in the lamina space (seat valve 11) and in the actuating chamber 9 of the switching element piston 10 can be set and, if necessary, a situation-dependent controllable clearance 17 can be taught.

reference list

1

switching element

2

inner slats

3

outer slats

4

inner disc carrier

5

Tooth profile of the inner disc carrier

6

outer disc carrier

7

Tooth profile of the outer disc carrier

8th

cylinder

9

chamber

10

switching element piston

11

seat valve

12

valve element

13

valve seat

14

cooling oil channel

15

ring groove

16

end plate

17

clearance

20

elastic element

21

passage opening

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102014226517 A1 [0009]
• DE 102019218519 A1 [0010]

Claims (7)

Switching element for actuating wet-running multi-disc clutches or brakes, in particular in the drive train of electrically driven passenger cars, comprising a disk set with inner and outer disks (2, 3), an inner disk carrier (4) on which the inner disks (2) of the disk set are arranged in an axially displaceable manner , an outer disk carrier (6) on which the outer disks (3) of the disk set are arranged in an axially displaceable manner, the disk set being compressible by means of a shifting element piston (10) when the shifting element (1) is actuated, and on a surface facing away from the shifting element piston (10). end plate (16) arranged on the side of the plate pack comes to rest, a seat valve (11) which is inserted into the end plate (16), the seat valve (11) blocking an inflow of cooling oil to the plate pack when the switching element (1) is open and when it is closed Switching element (1) releases the inflow, and elastic elements (20), each z between inner discs (2) arranged adjacent to one another or between outer discs (3) of the disc pack arranged adjacent to one another, for separating outer and inner discs (3, 2) of the disc pack when the switching element (1) is open and the inflow of cooling oil to the disk set is blocked by the seat valve (11), characterized in that the seat valve (11) can be controlled in such a way that a defined residual pressure of the cooling oil is maintained in the volume of the disk set, which essentially replaces a preload spring force required to return the switching element piston (10). when the inflow of cooling oil to the disk set is blocked by the seat valve (11), and an oil pressure generated in the chamber (9) of the switching element piston (10) by means of control via actuating valves for the pressure oil of the switching element (1) against the defined residual pressure of the cooling oil can be adjusted in the plate pack, so that when a pressure point is taught in, the pre-las t spring force of the switching element piston (10) for an open state of the switching element (1) a narrower clearance (17) compared to the stiffness of the preload springing can be achieved and adjusted. switching element after claim 1 , characterized in that one or more elastic elements (20), which are present for separating the outer disks (3) of the disk pack, are used as the preload spring. switching element after claim 2 , characterized in that the elastic elements (20) are ring-shaped or partially ring-shaped as an elastomer part. switching element after claim 2 , characterized in that the elastic elements (20) are designed as annular wave springs made of corrugated flat or round wire. switching element after claim 1 , characterized in that the control of the actuating valves for the pressure oil of the switching element (1) is designed to vary the size of the clearance (17) depending on the situation. switching element after claim 5 , characterized in that the control of the actuating valves for the pressure oil of the switching element (1) depending on critical frequency ranges, which can stimulate the movement of the slats, is set up to adapt the size of the clearance (17). switching element after claim 5 , characterized in that when controlling the actuating valves for the pressure oil of the switching element (1) for the adjusted setting of a narrower clearance (17), the installation space of the cylinder for the switching element piston (10) is designed to be shortened.

Images